﻿/* Copyright 2007-2008 dnAnalytics Project.
 *
 * Contributors to this file:
 * Marcus Cuda
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 
 * * Redistributions of source code must retain the above copyright notice, this 
 *   list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice, 
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * * Neither the name of the dnAnalytics Project nor the names of its contributors
 *   may be used to endorse or promote products derived from this software without
 *   specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
 * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;

namespace dnAnalytics.Random
{
    internal class MklRandomNumberGenerator
    {
        private readonly double[] mBuffer = new double[Control.RandomNumberGeneratorBufferSize];
        private readonly int mBufferSize = Control.RandomNumberGeneratorBufferSize;
        private readonly uint mId;
        private int mCurrent;
        private bool mDisposed;

        public MklRandomNumberGenerator(MklRngMethod method, int seed)
        {
            mId = SafeNativeMethods.create_generator((int) method, (uint) seed);
            int status = SafeNativeMethods.call_generator(mId, mBufferSize, mBuffer);
        }

        ~MklRandomNumberGenerator()
        {
            if (!mDisposed)
            {
                Dispose();
            }
        }

        /// <summary>
        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            if (!mDisposed)
            {
                mDisposed = true;
                SafeNativeMethods.delete_generator(mId);
                GC.SuppressFinalize(this);
            }
        }

        /// <summary>
        /// Returns a random number between 0.0 and 1.0.
        /// </summary>
        /// <returns>
        /// A double-precision floating point number greater than or equal to 0.0, and less than 1.0.
        /// </returns>
        public double Sample()
        {
            if (mCurrent < mBufferSize)
            {
                return mBuffer[mCurrent++];
            }
            int status = SafeNativeMethods.call_generator(mId, mBufferSize, mBuffer);
            mCurrent = 0;
            return mBuffer[mCurrent++];
        }
    }
}